LTE (long term evolution) project, which is the biggest new technology research and development project initiated by the 3GPP (3rd Generation Partnership Project) in recent two years, improves and enhances the 3G air access technology. Compared with the 3G, the LTE has more technical advantages which are embodied in various aspects, such as higher user data rate, packet transfer, reduced system delay, improved system capacity and coverage, and reduced operating costs and so on.
The downlink of the LTE adopts the OFDM technology which has characteristics of high spectrum utilization rate and anti-multipath interference and so on. An OFDM system can effectively resist the influence brought by wireless channels. In general, an OFDM system is provided with a plurality of antennae and each antenna has a plurality of pilot positions. The uplink transmission solution of the LTE adopts an SC-FDMA (single carrier frequency division multiple access) system with a cyclic prefix. In the transmission solution of the SC-FDMA system with the cyclic prefix adopted for the uplink, a DFT (discrete Fourier transformation) is used to acquire a frequency-domain signal, then frequency spectrum shift is performed by inserting zero symbols (nil symbols) into the frequency-domain signal, and the signal after being shifted is processed through IFFT (inverse fast Fourier transformation) (therefore, the SC-FDMA system is also called as a DFT-S-OFDM (discrete Fourier transformation spread orthogonal frequency division multiplexing) system), so that the peak-to-average power ratio of a transmitting terminal can be reduced.
A symbol timing offset can result in a phase rotation in the frequency domain, and can accumulate the phase along with the frequency-domain symbols. The timing offset in the frequency domain can increase the sensitive degree of the OFDM to a time delay spread, with the result being that the tolerable time delay spread of the system will be lower than a designed value. In order to reduce this negative influence to the most extent, the timing offset needs to be decreased to the most extent. Therefore, the timing offset needs to be estimated, and further corrected.
The protocol 3GPP TS 36.213: “Evolved Universal Terrestrial Radio Access (E-UTRA); Physical layer procedures” provides relevant contents on how to align and report the timing offset (TA). According to a received uplink signal, a base station measures an uplink synchronization timing offset value of a UE (user equipment), and sends the timing offset alignment value (timing alignment, TA) down to the UE. Then the UE adjusts the uplink transmission timing of its own according to the received value to realize the uplink synchronization process. Therefore, the timing offset estimation is an indispensable part of the LTE system.
The symbol timing offset has a corresponding relation with sub-carrier phases. As the timing changes, corresponding changes happen to the symbol phases on the sub-carriers. The timing offset t0 at a sample interval will generate the phase offset between two adjacent sub-carriers in the frequency domain as follows:
      φ    0    =                    2        ⁢        π            N        ⁢                  t        0            .      
Where N is the number of FFT (fast Fourier transformation) points corresponding to a system sampling frequency. The phase offset will accumulate linearly along with the increase of carrier distance, and can also generate a phase reversal when the accumulation comes to a certain extent.
The existing timing offset estimation technology is relatively sensitive to noises, can not provide good timing offset estimation performance under a low signal-to-noise ratio, and can not reduce the influence of the timing offset on the receiver performance.